Bright stock base oil blend

ABSTRACT

A method is disclosed for making a bright stock base oil blend meeting API Group II specifications. The method comprises blending (a) a major amount of a petroleum-derived bright stock component having kinematic viscosity at 100° C. of from 20 to 50 mm 2 /s with a sufficient amount of (b) a propylene oligomer component having a viscosity index of from 30 to 60, to provide a bright stock base oil blend having a higher viscosity than the petroleum-derived bright stock component and a higher viscosity index than the propylene oligomer component.

TECHNICAL FIELD

This disclosure is directed to bright stock base oil blends meeting APIGroup II specifications and methods for preparing the same.

BACKGROUND

High viscosity oils of improved quality are in general demand for avariety of applications including marine oils, mono-grade motor oils,gear oils, railroad engine oils, farm equipment oils, and greases. Highviscosity oils generally require some bright stock in their formulation,the amount of which depends on the product. In typical formulations,Group I bright stock is used. One problem with Group I bright stock isthat it is not a distillate and, therefore, is typically of low quality,particularly with respect to oxidation stability. Moreover, the supplyof Group I bright stock is diminishing, especially as Group I base oilplants are being shut down.

A Group II bright stock would have significant value in the marketplace,especially as a blending component with other Group II base oils.Methods for making such a bright stock are limited, usually requiringhydrocracking and solvent dewaxing of petroleum residual fractions.Residuum streams are generally difficult to process for lubricant baseoils.

U.S. Pat. No. 7,776,206 discloses a process for making a Group II brightstock using deep-cut distillation, which employs a distillate fractionto make the bright stock, rejecting the heavy aromatics most difficultto hydrocrack and stabilize, as well as the heavy wax most difficult toisomerize, in the distillation bottoms. The light fraction ishydrocracked to raise the viscosity index (VI) and to reduce theconcentration of nitrogen and sulfur, then dewaxed to give a Group IIbright stock with low pour and cloud points. In order to get the highviscosity required, a wiped film evaporator (WFE) is used in combinationwith vacuum distillation. While WFEs are used commercially and areavailable in the marketplace, their throughput size is limited.

U.S. Pat. No. 8,124,821 discloses a method for making a bright stock byoligomerization of propylene using an ionic liquid catalyst. Whilebright stock produced from propylene oligomerization has high viscosity,high oxidation stability and low pour and cloud points, the VI is low(e.g., less than 60). Co-oligomerization of propylene with a longernormal alpha-olefin (NAO), such as 1-octene or 1-decene, can produce ahigher VI bright stock, but the NAO feed can be expensive and in shortsupply. It would be advantageous to find another way get the VI up to atleast 80, producing a Group II bright stock. Since the propyleneoligomer is highly paraffinic, it would be advantageous have somecycloparaffinic and/or aromatic character to provide better additivesolubility and seal swell properties.

Improved processes for producing bright stocks meeting API Group IIspecifications are needed. It has been found that bright stock preparedby propylene oligomerization is particularly advantageous for blendingwith marginal quality petroleum-derived Group II bright stock to providea bright stock blend which meets minimum viscosity requirements and hasacceptable VI, good additive solubility, and improved low temperatureproperties.

SUMMARY

In one aspect, there is provided a method for making a bright stock baseoil blend meeting API Group II specifications comprising: blending (a) amajor amount of a petroleum-derived bright stock component havingkinematic viscosity at 100° C. of from 20 to 50 mm²/s with a sufficientamount of (b) a propylene oligomer component having a viscosity index offrom 30 to 60, to provide a bright stock base oil blend having a higherviscosity than the petroleum-derived bright stock component and a higherviscosity index than the propylene oligomer component.

DETAILED DESCRIPTION

The following terms will be used throughout the specification and willhave the following meanings unless otherwise indicated.

The term “petroleum-derived” means that the product, fraction, orblending stock originates from or is produced at some stage from apetroleum-based source.

A “bright stock” is a heavy base oil having an initial boiling point ofgreater than 900° F. (482° C.) and a kinematic viscosity at 100° C. ofat least 15 mm²/s (e.g., from 15 to 100 mm²/s).

An “oligomer” refers to compositions having from 2 to 100 monomer units.A “monomer” refers to one of the basic structural units of a polymer oroligomer. In the case of a homo-oligomer, a single repeating structuralunit forms the oligomer. In the case of a co-oligomer, two or morestructural units are repeated—either in a pattern or randomly—to formthe oligomer.

The term “Group I” refers to a base oil having a saturates content ofless than 90% and/or a total sulfur content of greater than 0.03% andhas a viscosity index of greater than or equal to 80 and less than 120,using the ASTM methods specified in Table E-1 of American PetroleumInstitute (API) Publication 1509.

The term “Group II” refers to a base oil having greater than or equal to90% saturates and less than or equal to 0.03% sulfur and has a viscosityindex greater than or equal to 80 and less than 120, using the ASTMmethods specified in Table E-1 of American Petroleum Institute (API)Publication 1509.

The term “Group III” refers to a base oil which contains greater than orequal to 90% saturates and less than or equal to 0.03% sulfur and has aviscosity index greater than or equal to 120, using the ASTM methodsspecified in Table E-1 of API Publication 1509.

The term “base oil” as used herein shall be understood to mean a basestock or blend of base stocks which is a lubricant component that isproduced by a single manufacturer to the same specifications(independent of feed source or manufacturer's location); that meets thesame manufacturer's specification; and that is identified by a uniqueformula, product identification number, or both.

“Kinematic viscosity” is a measurement in mm²/s of the resistance toflow of a fluid under gravity, determined by ASTM D445.

“Viscosity index” is an empirical, unit-less number indicating theeffect of temperature change on the kinematic viscosity of an oil. Thehigher the VI of the oil, the lower its tendency to change viscositywith temperature. VI is measured according to ASTM D2270.

“Pour point” is a measurement of the temperature at which a sample willbegin to flow under certain carefully controlled conditions, which canbe determined as described in ASTM D5950.

“Cloud point” is a measurement of the temperature at which a lube oilsample begins to develop a haze as the oil is cooled under specifiedconditions, which can be determined as described in ASTM D5773.

Petroleum-Derived Bright Stock Component

Petroleum-derived bright stock constitutes a bottoms fraction which hasbeen highly refined and dewaxed. Typical petroleum-derived bright stockscan be prepared from deasphalted oil, hydrocracked petroleum residuumstream, and heavy coker products.

The petroleum-derived bright stock can be a conventionalpetroleum-derived bright stock, an unconventional petroleum-derivedbright stock, or a mixture thereof. Conventional petroleum-derivedbright stock has a viscosity index of less than 120 (e.g., from 80 toless than 120). Unconventional petroleum-derived bright stock, such asbright stock derived from Daqing crude, has a viscosity index of atleast 120 (e.g., from 120 to 160, or from 120 to 140).

In one embodiment, the petroleum-derived bright stock is a hydrocrackedand dewaxed light distillate fraction having a distillation cut point inthe range of 1150° F. to 1300° F. (621° C. to 704° C.), as described inU.S. Pat. No. 7,776,206. The cut point is the temperature at which thereare equal amounts of material overlapping from adjacent cuts. When datais not available for one of both adjacent cuts, cut point estimates arethe 10 and 90 percent points on the distillation curve.

The petroleum-derived bright stock has a kinematic viscosity at 100° C.(KV₁₀₀) of at least 15 mm²/s (e.g., at least 20 mm²/s, at least 25mm²/s, at least 30 mm²/s, from 15 to 60 mm²/s, from 15 to 45 mm²/s, from20 to 60 mm²/s, from 20 to 45 mm²/s, from 25 to 60 mm²/s, from 25 to 45mm²/s, from 30 to 60 mm²/s, or from 30 to 45 mm²/s).

The petroleum-derived bright stock can have a high viscosity index, suchas at least 80 (e.g., from 80 to 145, from 80 to 130, from 80 to lessthan 120, from 80 to 110, from 80 to 100, from 80 to 90, from 85 to 145,from 85 to 130, from 85 to less than 120, from 85 to 110, from 85 to100, from 90 to 145, from 90 to 130, from 90 to less than 120, from 90to 110, from 100 to 145, from 100 to 130, or from 100 to less than 120).

The petroleum-derived bright stock can have low a pour point, such as 0°C. or less (e.g., −5° C. or less, −10° C. or less, −20° C. or less, from0° C. to −25° C., from −5° C. to −25° C., or −10° C. to −25° C.).

The petroleum-derived bright stock can have a cloud point of 15° C. orless (e.g., 10° C. or less, from 0° C. to 15° C., from 0° C. to 10° C.,or from 5° C. to 15° C.).

The petroleum-derived bright stock can be a Group II base oil or a GroupIII base oil.

Propylene Oligomer Component

The propylene oligomer disclosed herein can be synthesized byoligomerizing propylene in the presence of an ionic liquid catalyst. Thepropylene can come from a number of sources, including: as a byproductfrom the steam cracking of liquid feedstocks such as propane, butane,gas condensates, naphtha and LPG; from off-gases produced in a FCC unitin a refinery; from propane dehydrogenation using a noble metalcatalyst; and by metathesis. Propylene supplies are increasing and thereis a demand for upgrading them into higher valued products such as baseoils.

Oligomerization conditions include temperatures between the meltingpoint of the ionic liquid catalyst and its decomposition temperature. Inone embodiment, the oligomerization conditions include a temperature offrom 0° C. to 100° C. and a pressure of from atmospheric pressure to1000 psig (0.10 to 6.89 MPa). The oligomerization can carried out incontinuous, batch or semi-batch mode.

A skilled artisan will recognize that depending on the process utilizedto produce the propylene oligomer, the as-produced propylene oligomerscan already be substantially saturated. For example, a process which iscarried out in the presence of hydrogen can produce an olefin oligomerwhich may or may not require a separate hydrogenation step to provide aproduct with the desired properties.

The propylene oligomer can comprise at least 70% propylene monomer units(e.g., at least 75% propylene monomer units, at least 80% propylenemonomer units, at least 85% propylene monomer units, at least 90%propylene monomer units, at least 95% propylene monomer units, or atleast 99% propylene monomer units). Alternatively, the propyleneoligomer can consist essentially of propylene monomer units.

The propylene oligomer can comprise a significant amount of hydrocarbonsboiling at 900° F. (482° C.) or higher. The level can be greater than 25wt. %, greater than 35 wt. %, or from 45 to 70 wt. %. Higher levels ofhydrocarbons boiling at 900° F. (482° C.) or higher are desired, asthere are increasingly limited amounts of base oils with theseproperties, especially as Group I base oil plants are being shut down.

In one embodiment which employs a high viscosity petroleum-derivedbright stock in the lubricating oil composition disclosed herein, asomewhat lower distillation cut point, such as 800° F. (427° C.), can betaken on the propylene oligomer thereby increasing yield and improvingeconomics because of the cost of propylene.

The propylene oligomer can have a kinematic viscosity at 100° C. of atleast 50 mm²/s (e.g., from 50 to 100 mm²/s or from 55 to 95 mm²/s).

The propylene oligomer can have a low viscosity index, such as 60 orless (e.g., from 30 to 60 or from 35 to 55).

The propylene oligomer can have a low pour point, such as −10° C. orless (e.g., from −10° C. to −60° C., from −10° C. to −40° C., or from−10° C. to −25° C.).

The propylene oligomer can have a low cloud point, such as point −25° C.or less (e.g., −40° C. or less, −45° C. or less, −50° C. or less, −55°C., −60° C. or less, from −40° C. to −60° C., from −45° C. to −60° C.,from −50° C. to −60° C., or from −55° C. to −60° C.).

In one embodiment, the propylene oligomer is a bright stock.

Bright Stock Base Oil Blend

In general, the relative amounts of the petroleum-derived bright stockand the propylene oligomer can be tuned to produce a bright stock baseoil blend with a desired balance between viscosity, viscosity index andcold temperature flow properties.

The petroleum-derived bright stock is typically present therein in amajor amount, i.e., an amount of greater than 50 wt. %, based on thetotal weight of the blend. In general, the blend will comprise from 90to 60% (e.g., from 90 to 65 wt. %, from 85 to 60 wt. %, from 85 to 65wt. %, or from 85 to 70 wt. %) of the petroleum-derived bright stockcomponent and from 10 wt. % to 40 wt. % (e.g., from 10 to 35 wt. %, from15 to 40 wt. %, from 15 to 35 wt. %, or from 15 to 30 wt. %) of thepropylene oligomer component, based on the total weight of the blend. Iftoo small an amount of the propylene oligomer is used, the blend may nothave acceptable viscosity index and/or low temperature properties. Iftoo much of the propylene oligomer is used, it may be more costly or theviscosity of the blend may be too high for practical use.

The bright stock base oil blend disclosed herein has a higher viscositythan that of the petroleum-derived bright stock component. Whenpropylene oligomer is present in the base oil blend in amounts of from10 to 40 wt. %, based on the total weight of the blend, the kinematicviscosity at 100° C. of the resulting base oil blend can be at least 3mm²/s higher (e.g., at least 5 mm²/s higher, at least 10 mm²/s higher,from 3 to 20 mm²/s higher, from 3 to 15 mm²/s higher, from 3 to 10 mm²/shigher, from 5 to 20 mm²/s higher, from 5 to 15 mm²/s higher, or from 5to 10 mm²/s higher) than the petroleum-derived bright stock component.The blend can have a kinematic viscosity at 100° C. of at least 28 mm²/s(e.g., at least 30, from 28 to 50 mm²/s, from 28 to 45 mm²/s, from 30 to50 mm²/s, or from 30 to 45 mm²/s).

The bright stock base oil blend disclosed herein has a higher viscosityindex than that of the propylene oligomer component. When propyleneoligomer is present in the base oil blend in amounts of from 10 to 40wt. %, based on the total weight of the blend, the viscosity index ofthe resulting base oil blend can be at least 20 higher (e.g., at least25 higher, from 20 to 50 higher, from 20 to 40 higher, from 25 to 50higher, or from 25 to 40 higher) than the propylene oligomer component.The blend can have a high viscosity index, such as at least 85 (e.g., atleast 90, from 85 to 140, from 85 to 130, from 85 to less than 120, from85 to 110, from 85 to 100, from 90 to 140, from 90 to 130, from 90 toless than 120, or from 90 to 110).

The bright stock base oil blend disclosed herein has improved coldtemperature flow properties than that of the petroleum-derived brightstock component. When propylene oligomer is present in the base oilblend in amounts of from 10 to 40 wt. %, based on the total weight ofthe blend, the pour point of the blend can be at least 1° C. lower(e.g., at least 2° C. lower, at least 3° C. lower, from 1° C. to 10° C.lower, from 1° C. to 5° C. lower, 1° C. to 3° C. lower, from 2° C. to10° C. lower, or from 2° C. to 5° C. lower) than that of thepetroleum-derived bright stock component. The blend can have a low pourpoint, such as −1° C. or less (e.g., from −1° C. to −25° C., from −5° C.to −25° C., or from −10° C. to −25° C.).

When propylene oligomer is present in the base oil blend in amounts offrom 10 to 40 wt. %, based on the total weight of the blend, the cloudpoint of the blend can be at least 1° C. lower (e.g., at least 2° C.lower, e.g., at least 3° C. lower, from 1° C. to 10° C. lower, from 1°C. to 5° C. lower, 1° C. to 3° C. lower, from 2° C. to 10° C. lower, orfrom 2° C. to 5° C. lower) than that of the petroleum-derived brightstock component. The blend can have a cloud point of 14° C. or less(e.g., 13° C. or less, 5° C. or less, from 13° C. to −15° C., or from 5°C. to −15° C.).

EXAMPLES

The following illustrative examples are intended to be non-limiting.

Example 1

Oligomerization of propylene was carried out using a supported liquidphase ionic liquid catalyst according to the procedure described in U.S.Pat. No. 8,729,329. The heavy viscous colorless oil was then analyzedfor boiling range, viscosity index, kinematic viscosity, pour point andcloud point. The products were analyzed for their boiling range bysimulated distillation analysis. The properties of the 900° F.+fractionare set forth are set forth in Table 1.

TABLE 1 KV₁₀₀, mm²/s 96.3 VI 58 Pour point, ° C. −15 Cloud point, ° C.−60

Example 2

A 300 cc autoclave was charged with 20 g of ionic liquid catalyst(1-butyl-pyridinium chloroaluminate ionic liquid catalyst), 0.1-1 g ofHCl and 20 g of n-hexane (as diluent) under nitrogen in a glove box. Theautoclave was sealed and removed from the glove box and cooled in a dryice bath and affixed to a propylene tank (>99% commercial grade) via aninlet that allows the flow of propylene into the reactor where 100 g ofpropylene was transferred to the reactor (autoclave). The reactor wasaffixed to an overhead stirrer. The reaction temperature was controlledby a thermocouple connected to a temperature control apparatus. Onceeverything was in place, the reaction began by slowly stirring thecharge in the reactor at 0° C. in a batch-style operation. The reactionwas exothermic and the rise in temperature was quick and sudden. Therise in temperature was controlled by immersing the autoclave in an icebath. The reaction temperature was kept at around 50° C. The pressure ofthe reaction began very high and decreased as the propylene wasoligomerized. The reaction was allowed to proceed for 15-30 minutes. Thereaction, then, was stopped and the reactor was allowed to cool to roomtemperature. The reaction was worked up by simply decanting off theorganic layer (the products). The remaining ionic liquid phase waswashed with hexane to remove all residual organics from the ionic liquidphase, and the wash was added to the original decant. The organic layerwas then washed thoroughly with water and dried over anhydrous MgSO₄ andthen filtered. The filtrate was concentrated on a rotary evaporator toremove hexane (used as solvent to extract oligomers from the catalyst).The heavy viscous colorless oil was then analyzed for boiling range,viscosity index, kinematic viscosity, pour point and cloud point. Theproducts were analyzed for their boiling range by simulated distillationanalysis. The properties of the 900° F.+fraction are set forth are setforth in Table 2.

TABLE 2 KV₁₀₀, mm²/s 56 VI 43 Pour point, ° C. 4 Cloud point, ° C. <−56

Example 3

A low viscosity bright stock was prepared from Daqing crude byhydroisomerization for use as a bright stock blending component. Theproperties of the Daqing bright stock are set forth in Table 3.

TABLE 3 KV₁₀₀, mm²/s 21.5 VI 137 Pour point, ° C. −21 Cloud point, ° C.15 Simulated Distillation, ° F., wt. % 0.5/5   897/960 10/30  989/105550 1108 70/90 1167/1253   95/99.5 1291/1338

Example 4

A bright stock blend was prepared which comprised 26 wt. % of thepropylene oligomer of Example 1 and 74 wt. % of the petroleum-derivedbright stock of Example 3. The properties of the petroleum-derivedbright stock, the propylene oligomer, and the bright stock blend aresummarized in Table 4.

TABLE 4 Petroleum- Derived Propylene Bright Stock Oligomer Blend AKV₁₀₀, mm²/s 21.5 96.3 26.6 VI 137 58 125 Pour point, ° C. −21 −15 −24Cloud point, ° C. 15 −60 13

This Example illustrates that the propylene oligomer effectively loweredthe pour point and cloud point and raised the viscosity by 5 mm²/s.Conducting the same experiment using more propylene oligomer would beexpected to produce a bright stock base oil blend having furtherimproved low temperature properties while keeping the VI above 90.

Example 5

Three bright stock blends were prepared from the propylene oligomer ofExample 1 and another low viscosity, petroleum-derived bright stock. Theproperties of the petroleum-derived bright stock, the propyleneoligomer, and the bright stock blends are summarized in Table 5.

TABLE 5 Petroleum- Derived Propylene Bright Stock Oligomer Blend B BlendC Blend D Wt. % Bright 85 80 67 Stock Wt. % Propylene 15 20 33 OligomerKV₁₀₀, mm²/s 23.6 96.3 28 30 35 VI 89 58 84 82 78 Pour point, ° C. 0 −15−1 −3 −4 Cloud point, ° C. 7 −60 4 2 1

Example 6

A bright stock blend was prepared which comprised 27 wt. % of thepropylene oligomer of Example 1 and 73 wt. % of a petroleum-derivedbright stock. The properties of the petroleum-derived bright stock, thepropylene oligomer, and the bright stock blend are summarized in Table6.

TABLE 6 Petroleum- Derived Propylene Bright Stock Oligomer Blend EKV₁₀₀, mm²/s 32.5 96.3 41.3 VI 96 58 87 Pour point, ° C. −9 −15 −12Cloud point, ° C. — −60 −12

This Example illustrates that the propylene oligomer effectivelyimproved the low temperature properties and raised the viscosity by 7.8mm²/s. Conducting the same experiment using less propylene oligomerwould be expected to produce a bright stock base oil blend having a VIabove 90 with improved low temperature properties.

Example 7

A bright stock blend was prepared which comprised 21 wt. % of thepropylene oligomer of Example 2 and 79 wt. % of the petroleum-derivedbright stock employed in Example 6. The properties of thepetroleum-derived bright stock, the propylene oligomer, and the brightstock blend are summarized in Table 7.

TABLE 7 Petroleum- Derived Propylene Bright Stock Oligomer Blend FKV₁₀₀, mm²/s 32.5 56 36 VI 96 43 88 Pour point, ° C. −9 4 −12

This Example illustrates that the propylene oligomer effectively loweredthe pour point and raised the viscosity by 3.5 mm²/s. Conducting thesame experiment using less propylene oligomer would be expected toproduce a bright stock base oil blend having a VI above 90 with improvedlow temperature properties.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Furthermore, all ranges disclosed herein are inclusive ofthe endpoints and are independently combinable. Whenever a numericalrange with a lower limit and an upper limit are disclosed, any numberfalling within the range is also specifically disclosed.

As used herein, the term “comprising” means including elements or stepsthat are identified following that term, but any such elements or stepsare not exhaustive, and an embodiment can include other elements orsteps.

Unless otherwise specified, the recitation of a genus of elements,materials or other components, from which an individual component ormixture of components can be selected, is intended to include allpossible sub-generic combinations of the listed components and mixturesthereof.

Any term, abbreviation or shorthand not defined is understood to havethe ordinary meaning used by a skilled artisan at the time theapplication is filed. The singular forms “a,” “an,” and “the,” includeplural references unless expressly and unequivocally limited to oneinstance.

All of the publications, patents and patent applications cited in thisapplication are herein incorporated by reference in their entirety tothe same extent as if the disclosure of each individual publication,patent application or patent was specifically and individually indicatedto be incorporated by reference in its entirety.

1. A method for making a bright stock base oil blend meeting API GroupII specifications comprising: blending (a) a major amount of apetroleum-derived bright stock component having kinematic viscosity at100° C. of from 20 to 50 mm²/s with a sufficient amount of (b) apropylene oligomer component having a viscosity index of from 30 to 60,to provide a bright stock base oil blend having a higher viscosity thanthe petroleum-derived bright stock component and a higher viscosityindex than the propylene oligomer component.
 2. The method of claim 1,wherein the blend comprises from 60 to 90% of the petroleum-derivedbright stock component and from 40 wt. % to 10 wt. % of the propyleneoligomer component, based on the total weight of the blend.
 3. Themethod of claim 1, wherein the blend comprises from 70 to 85% of thepetroleum-derived bright stock component and from 30 wt. % to 15 wt. %of the propylene oligomer component, based on the total weight of theblend.
 4. The method of claim 1, wherein the blend has a kinematicviscosity at 100° C. that is at least 3 mm²/s higher than that of thepetroleum-derived bright stock component.
 5. The method of claim 1,wherein the blend has a viscosity index that is at least 20 higher thanthat of the propylene oligomer component.
 6. The method of claim 1,wherein the blend has a pour point that is at least 1° C. lower thanthat of the petroleum-derived bright stock component.
 7. The method ofclaim 1, wherein the blend has a cloud point that is at least 1° C.lower than that of the petroleum-derived bright stock component.
 8. Themethod of claim 1, wherein the petroleum-derived bright stock componenthas a viscosity index of from 80 to less than
 120. 9. The method ofclaim 1, wherein the petroleum-derived bright stock component has aviscosity index of from 120 to
 145. 10. The method of claim 1, whereinthe petroleum-derived bright stock component has a pour point of 0° C.or less.
 11. The method of claim 1, wherein the petroleum-derived brightstock component has a cloud point of 15° C. or less.
 12. The method ofclaim 1, wherein the propylene oligomer component has a kinematicviscosity at 100° C. of from 50 to 100 mm²/s.
 13. The method of claim 1,wherein the propylene oligomer component has a pour point of −10° C. orless.
 14. The method of claim 1, wherein the propylene oligomercomponent has a cloud point of −25° C. or less.